In the mid-1950s, NATO officials became concerned with the possibility
that Soviet nuclear weapons could obliterate Allied aircraft sitting
on the ground at their airfields in a surprise attack, leaving NATO
powerless to retaliate. One of the potential cures for this problem
was to disperse aircraft in hardened shelters far away from targeted
airfields, and having these aircraft launched by rocket propulsion
from special platforms. The concept was known as Zero-Length Launch,
or ZEL for short.